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采用低碳微合金成分体系和直接淬火工艺,研制了屈服强度超过800MPa,抗拉强度超过950MPa,-40℃冲击功超过90J且焊接裂纹敏感性指数Pcm小于0.2%的40mm低焊接裂纹敏感性厚板。厚板的微观组织为厚度小于1μm贝氏体铁素体板条和沿板条界面分布的M/A组元,贝氏体板条内部有亚板条。随着终冷温度的降低,贝氏体铁素体板条变细。不同终冷温度钢板的贝氏体板条内部均存在高密度位错。试验用钢的贝氏体形核长大过程可以用扩散机制较好的解释。
A 40mm low welding crack sensitivity of over 800MPa, tensile strength of over 950MPa, impact energy of -40 ℃ of over 90J and weld crack sensitivity index (Pcm) less than 0.2% was developed by using low carbon micro-alloy composition system and direct quenching process board. The microstructure of the slab is a bainitic ferrite slab with a thickness of less than 1μm and M / A component distributed along the slab interface. The bainite slab has sub-slabs therein. As the finish cooling temperature decreases, the bainitic ferrite strip becomes thinner. High-density dislocations exist in the bainite slabs of different final cold-tempered steel plates. The bainitic nucleation and growth of the test steel can be better explained by the diffusion mechanism.